1. Field of the Invention
The subject invention is directed to flexible couplings, and more particularly to a flexible diaphragm coupling for rotating shaft components, which is configured to tolerate axial forces and the axial bending stress distribution associated therewith.
2. Description of Related Art
Flexible couplings for connecting two rotating shafts to one another, to transmit torque while accommodating axial and/or angular misalignment of the shafts have been used in aerospace applications for many years. These devices often use one or more contoured diaphragms welded or otherwise secured together to form a flexible coupling mounted between driving and driven shaft components.
For example, commonly assigned U.S. Pat. No. 5,158,504 to Stocco describes a coupling having plural contoured diaphragms welded together to form a flexible connection between a driving shaft and a driven shaft. Those prior art diaphragms were configured to accommodate large axial deflections without over-stressing the diaphragm material. They were contoured to be thinnest in a location midway between their hub and rim, where the bending moment developed by axial deflections was determined to be smallest. This ensured that stress levels would be minimized throughout the diaphragm. The diaphragm profile disclosed in U.S. Pat. No. 5,158,504 has been employed with great success for many years in a variety of aerospace shaft coupling applications.
Recently, aerospace shaft coupling applications have arisen with new and different loading requirements than contemplated in U.S. Pat. No. 5,158,504. In particular, there has now become a need in the art for a contoured diaphragm element that can tolerate both linear and nonlinear deflections produced by axial force loading. More particularly, in addition to tolerating a first restorative force generated by the linear axial spring rate of the diaphragm, as contemplated in U.S. Pat. No. 5,158,504, the new diaphragm profile must also tolerate a second restorative force involving cubic non-linear membrane stresses generated when the axial load stretches the diaphragm in a radial direction. This design requirement was neither contemplated nor appreciated in U.S. Pat. No. 5,158,504.